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123C3 NATIONAL LIBRARY mst BIBLIOTHEQUE NATIONALE OTTAWA mWm OTTAWA NAME OF AUTHOR fefeflf '* . Q'.. HO*?. f>J.W ?*/ TITLE OF THESIS F^P.VATI9tf,. .PtflW./A?.. ?fi.. # .™.4£'./Yf: fMTfASH.. .^f P.P.V.L.^ ?.*?:. UNIVERSITY pA>.Hoy5i£ DEGREE" FOR WHICH THESIS WAS PRESENTED .?f;\ H". YEAR THIS DEGREE GRANTED W .T?r Permission is hereby granted to THE NATIONAL LIBRARY OF CANADA to microfilm this thesis and to lend or sell copies of the film. The author reserves other publication rights, and neither the thesis nor extensive extracts from it may be printed or otherwise reproduced without the author's written permission. (signed).. Os^r^/f.^^.^^yrr^fr PERMANENT ADDRESS: 7 P^py^. fr^-. •. • .....> DATED.... $jfaJ<fy• — 19 72- NL-91 (10-6tf) PRODUCTION DYNAMICS OF A MARINE FLATFISH POPULATION: AN ENERGETICS MODEL by James C. MacKinnon Submitted in partial fulfillment of the requirements for the DEGREE OF DOCTOR OF PHILOSOPHY at DALHOUSIE UNIVERSITY March 15, 1972 Approved • jv • * • • • y • • • @ James C. MacKinnon 1972 - ii - DALHOUSIE UNIVERSITY Date April 30, 1972 Author James C. MacKinnon Title Production dynamics of a marine flatfish population: an energetics model Department or School Oceanography Degree Ph.D. Convocation - May Year 1972 Permission is herewith granted to Dalhousie University to circulate and to have copied, at its discretion, the above title upon the request of individuals or institution. 1/vyW' /C }v cu_, fy^VT^rhi Signature of Author EXTENSIVE QUOTATION OR FURTHER REPRODUCTION OF THIS MATERIAL FOR COMMERCIAL PURPOSES BY PERSONS OR AGENCIES OTHER THAN DALHOUSIE UNIVERSITY MAY NOT BE MADE WITHOUT THE EXPRESS PERMISSION OF THE AUTHOR. - iii - PRODUCTION DYNAMICS OF A MARINE FLATFISH POPULATION: AN ENERGETICS MODEL by J. C. MacKinnon - iv - TABLE OF CONTENTS Page ABSTRACT vii ACKNOWLEDGEMENTS ix INTRODUCTION X SECTION A: A PRODUCTION MODEL FOR ESTIMATION OF EQUILIBRIUM YIELDS FROM A MARINE FLATFISH POPULATION 1 Introduction 3 Ecology of American Plaice 6 Design of the Production Model 13 1. Structure of the Model 13 a. General Features 13 b. Metabolic Model for an Individual Fish 17 2. Choice of Parameters 22 3. Computer Program Description 26 Results and Discussion 28 1. Productivity of St. Margaret's Bay Plaice 28 2. Effects of Fishing on Stock Structure and Productivity 36 3. Potential Yields from Demersal Fish Stocks 46 References 56 SECTION B: SUMMER STORAGE OF ENERGY AND ITS USE FOR WINTER METABOLISM AND GONAD MATURATION IN AMERICAN PLAICE 81 Introduction 83 - v - Materials and Methods 84 Sampling Scheme 84 Sample Processing 86 Drying Methods 87 Calorimetry 87 Results 89 Seasonal Changes in Condition 89 Annual Gonad Weight Cycle 90 Dry Weight of Materials 92 Energy Content of Materials 94 Seasonal Energy Storage Patterns 94 Discussion 98 Energy Content of American Plaice Materials 98 Energy Storage and Conversion Processes 100 Energy Storage and Reproduction 106 The Strategy of Summer Feeding Ill References 116 SECTION C: RELATIONSHIP BETWEEN METABOLISM AND GROWTH RATE OF AMERICAN PLAICE 125 Introduction 127 Materials and Methods 130 Results 132 Discussion 135 Metabolic Adaptation of American Plaice. 135 Relationship Between Metabolism and Growth 139 - vi - References 148 APPENDIX: Main Features of the Production Model and of Beverton-Holt Yield Models: A Comparison - vii - ABSTRACT The seasonal pattern of production processes in the American plaice (Hippoglossoides platessoides) population of St. Margaret's Bay, Nova Scotia was analyzed with a model based upon energy principles. Results are presented for field and laboratory investigations designed to provide energetics data required by the model. Estimates derived from the model are given for seasonal and annual energy flows of the population in its present unexploited state and in states that might be attained as a result of fishing. Annual net production and ingestion of the unexploited population were estimated at 2.3 kcal/m2 and 11.0 kcal/m2 respectively. Larvae and 0+ fish accounted for 20% of total ingestion by the population and 34% of net production while their biomass constituted only 4% of the population total. Production during summer months by fish aged 1 and up exceeded the corresponding net annual production by a factor of two as a result of the use of stored energy for metabolism and gonad maturation during winter. Highest fishing yields are predicted by the model for equilibrium states where it is assumed that population response mechanisms have been able to maintain ingestion at its pre-exploitation value whereas lower yields are obtained when situations of less complete response are considered. The reaction of the population to fishing is in accord witn theoretical ecological considerations which postulate increased productivity in association with decreased diversity and homeostatic capacity as expoitation is intensified. - ix ~ ACKNOWLEDGEMENTS The major portion of this research was completed at the Marine Ecology Laboratory of the Fisheries Research Board of Canada. I wish to thank Dr. L. M. Dickie, the Director, for permission to use the equipment and other facilities of the Laboratory. I also wish to express my appreciation to the many staff members of the Laboratory for advice and assistance in connection with practical aspects of the work and for many stimulating discussions, scientific and otherwise. I am particularly indebted to Dr. K. H. Mann, my supervisor, who provided very considerable assistance throughout all stages of the work. His advice and encouragement served to make the whole period of the research a thoroughly rewarding personal experience. The final draft of the manuscript was read by Dr. G. A. Riley, Dr. I. A. McLaren and Dr. L. M. Dickie. Valuable criticisms of earlier drafts were provided by various members of the Laboratory staff. Typing of the manuscript was done by Mrs. N. Gillespie and Miss B. Hare. In addition to the equipment and facilities made available by the Marine Ecology Laboratory, financial support for the research was provided through scholarships from the National Research Council of Canada and Dalhousie University. INTRODUCTION An analysis of the production process is a primary objective of theoretical models of exploited fish populations. This analysis involves the application of energy principles to all components of the fish population system (eggs, larvae, immature and mature fish) and to interactions of the system with other components of the particular ecosystem of which it is a part. The energetics considerations must be integrated with the "traditional" population dynamics analysis of changes in numbers via birth and death processes, and attention should also be given to the ability of the population to adapt to environmental change, including exploitation, by a variety of regulatory mechanisms. These statements summarize the main concepts underlying a production model which is developed in this thesis; the model is used for evaluating changes in production dynamics and fishing yields obtainable from exploitation of stocks of a common Atlantic flatfish species. Details concerning structure of the production model and choice of parameter values are presented in the first section of the thesis along with a discussion of model predictions concerning the changes in production dynamics which are caused by fishing. Supporting data obtained in field and laboratory studies are presented in two subsequent sections. Emphasis on production and the use of energy principles in the analysis of fish population dynamics has evolved in - xi - parallel with the emergence of energetics as an important aspect of ecological research. The early papers of Winberg1 gave a major impetus to the use of energetics concepts in studies of fish metabolism, growth ana food requirements. Paloheimo and Dickie subsequently explored in greater detail the relationships between food and growth of individual fishes while Mann extended the use of energetics methods to the fish population level. In more recent papers, the ecological context of fish populations as production systems has been emphasized and "food-chain" models for tne assessment of fishery resources have become widely used. Earlier models such as those of Beverton and Holt which were concerned with the dynamics of exploited fish populations focused attention on yield and its relationship with parameters affecting the processes of growth, recruitment and mortality. A detailed comparison of features of the present model with those of Beverton and Holt models is included as an appendix of the thesis. In the yield models of Beverton and Holt the effects of fish/fishery interactions were examined in detail whereas other ecological relationships, such as those between the population and its food supply, were given relatively little attention. The simple population production models of Paloheimo and Dickie were the first to demonstrate how References to papers by authors mentioned in this introduction are found after the three sections of the thesis. - xii - energetics concepts could be used to aevelop relationships among yield, production, physiological parameters and characteristics of the food supply and the physical environment. The production model presented in this thesis is an extension of this line of research and includes, in addition, consideration of regulation mechanisms whose adaptive significance has been emphasized by Russian researchers such as Nikolsky. - 1 SECTION A A Production Model for Estimation of Equilibrium Yields from a Marine Flatfish